First, confirm the pool is really losing water
Rain and melting snow can collect on top of a solid winter cover, and that water is separate from the water in the pool. Before assuming a leak, make sure the level beneath the cover has actually fallen.
Safety comes first. Never walk on a pool cover, stand on snow or ice near the pool, or loosen an anchored cover just to check the level. A cover is not designed to hold a person, and a fall into a covered pool can be fatal. If you cannot see the water level from the edge or through a safe opening, contact the company that closed the pool.
If you can see the level safely:
- Mark or photograph the level against a fixed point such as a tile line, skimmer or return.
- Recheck after several days.
- Keep notes on weather, temperature and any water you added.
A steady decline across several checks is better evidence of a leak than a single observation.
Rule out the cover pump and other non-leak causes
Pools that use a solid cover often have a cover pump to remove surface water. A pump that stays plugged in can run continuously, and if the cover has holes or the pump sits too close to one, it may pump pool water out. A discharge hose that creates a siphon can do the same. Pool professionals report seeing pools in spring that were mistaken for leaking when they had been pumped down.
Check that:
- The pump is positioned so it removes only surface water from the cover.
- The cover has no holes near the pump.
- The discharge hose is not siphoning back or draining the pool.
Evaporation also happens under covers, though much less than in summer. A very slow decline over months may not mean a leak.
Should you add or remove water?
Be careful. Adding water may restore support under a safety cover, but it does not fix a leak, and overfilling above the winter level can let water into the skimmer or other areas meant to stay dry. Removing water is also not something to do on your own without advice.
The right action depends on pool type, cover type, how much water is missing and how the pool was winterized. Ask the company that closed your pool, or a leak detection professional, before making a large change. If a solid cover is sagging into the pool or a safety cover looks unsupported, call them promptly.
Will an inground pool collapse without water in winter?
Pools are built to be full or close to it. Without enough water, a pool with high groundwater or saturated soil around it can be pushed upward by hydrostatic pressure, and in extreme cases a shell may lift or crack. Without water the cover also loses support. For these reasons, pool manufacturers and contractors generally advise against letting a pool drain significantly.
This does not mean a small drop in water level will cause a collapse. It does mean a large or continuing loss deserves quick professional attention, particularly if you have a vinyl liner pool (liners can wrinkle or be damaged when the water is low) or a high water table.
Where winter pool leaks usually come from
Winterization blocks off plumbing lines, but it does not seal the whole pool. Water can still escape from:
- A vinyl liner, especially around cut-outs for stairs, returns, lights or skimmers.
- The skimmer body or the joint where it meets the pool wall.
- Light niches, return fittings and the main drain.
- Cracks in a concrete or gunite shell (see how to fix a crack in a pool).
- Plumbing lines, if they were not fully drained or plugged, or if freezing damaged them.
Gunite pools are often said to leak less from the shell itself than from fittings and skimmers, while liners can leak from many places. If the water stops dropping at a certain level, that can hint at where the leak is, although it does not prove it.
Can a closed pool be tested in winter?
Some leak detection companies do work on closed pools, depending on climate, cover type and access. Others prefer to wait until the pool is open. Ask whether they test in winter and what they need to know. It helps to have answers ready:
- Pool type (gunite, vinyl or fiberglass) and age.
- Cover type (solid with water bags or safety cover).
- Whether the pool lost water during the season.
- Current water level relative to the skimmer and returns.
How much does it cost to fix a pool leak?
Costs vary widely with the leak location, pool type, region and whether detection is needed first. A simple liner patch or fitting repair can be modest, while a structural crack or replumbing can run much higher. Get written quotes from more than one qualified company rather than relying on a general figure.
Are pool leaks covered by insurance?
Often not fully. Many homeowners policies exclude gradual leaks and wear and tear, though some cover sudden, accidental damage or the cost of finding the source in certain cases. Policies differ, so read yours or ask your insurer or agent before work begins, and keep photos and records.
What to do in spring
If the water level held steady through winter after some early loss, you may still want a check when you open the pool. When you open it:
- Check fittings, skimmers and lights before filling to the normal level.
- Run a bucket test to compare pool and bucket levels.
- Look for wet ground or soft spots around the pool and equipment pad. Wet ground can also come from a household supply line; see water main leak to house.
- For plaster damage you can see, see our notes on DIY pool plaster repair.
When to call a professional
Call a pool company or leak detection specialist if:
- The water level keeps dropping.
- A solid cover is slipping into the pool or a safety cover is losing support.
- You suspect a siphon or cover pump problem and are unsure how to correct it.
- You see wet ground, sinkholes or shifting around the pool.
- You need to drain or lower the water.
Do not wait until spring without a plan if the loss is ongoing.